Reversible hydraulic pump or motor



Aug. 22, 1961 D. s. OLIVER REVERSIBLE HYDRAULIC PUMP OR MOTOR Filed May 19, 1960 fielfier'z j Oliver United States Patent 2,996,997 REVERSIBLE HYDRAULIC :PUMP R MOTOR Delbert S. Oliver, Wooster, Ohio, assignor to Borg -Warner Corporation, Chicago, Ill., a corporation of Illinois Filed May '19, 1960, Ser. No. 30,199 7 Claims. (Cl. 103-126) This invention relates to hydraulic apparatus and more particularly to a reversible hydraulic pump or motor of the pressure loaded, 'intermeshinggear type.

It is a primary object of this invention to provide a new and improved pressure loaded gear pump or motor which is readily reversible.

It is another object of this invention to provide a symmetrical pressure loaded gear pump or motor which is equally efiicient with fluid flow in either of two directions.

It is a further object of this invention to provide a gear pump or motor in which the pressure loading areas are eccentric with respect to the central axis of the apparatus to provide ofiset loading.

It is yet another object of this invention to provide a gear pump or motor having a loading plate-movablein response to outlet pressure for pressure loading the journal bearings.

It is a still further object of this invention to provide a gear pump or motor having an axiallymovable loading plate for loading the journal bearings and a pair of spring loading dual purpose valves mounted in the loading plate and alternatively operable, dependent on the direction of flow, to check the flow of high pressure fluid and to relieve low pressure fluid which has accumulated between the loading plate and the journal bearings due to leakage through the journal bearings.

With these and other objects in view, the present invention contemplates a gear pump formed of a chambered housing having two journaled, intermeshing, displacing gears mounted for rotation therein by means of individual journal bearings supporting each gear journal and capable of independent axial movement thereon. End covers are secured to the housing to retain the gears and journal bearings within the housing and in pumping relationship while-the journal bearings and the walls of the housing cooperate to define a pumping chamber surrounding the intermeshing gears. A loading plate is interposed between one of the end covers and the adjacent journal bearings. A sealing member is interposed between the loading plate and the end cover to define a pressure loading cavity on each sidethereof. A pair of reed-type valves are mounted in the loading plate, one on each side of the sealing member, and are spring loaded in such a direction as to precludethe flow of high pressure fluid from the pressure loading cavities through the loading plate while permitting flow of low pressure fluid through the loading plate and into either of the pressure loading cavities. The housing is provided with a pair of ports on opposite sides thereof, which ports serve as either inlet or outlet depending upon the direction of rotation of the gears. The interior of the housing is provided with cut-away portions which permit fluid communication between each port and the pressure loading cavity which is located on the same side of the central axis of the pump.

Other objects, advantages and novel features of the invention will become apparent upon consideration of the following detailed description when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is .a sectional view of an apparatus embodying the principal features of the invention and illustrating to advantage the loading plate and spring loaded sealing member;

FIG. 2 is. a sectional view taken. along the lines .22.;of

FIG. 1 and illustrating :the arrangement of .thezsealing' member, the spring loaded reedstype valves, and the .cutaway portions of the .housinguwhich serve to communicate the pressureloadingcavities 'with the inletandtoutlet ports;

FIG. 3 is a sectional view taken along lines ,3+3 "of FIG. 2 and illustrates to advantage the construction of the reed-'type-valves; and

FIG. 4 is a sectional view takenalong the lines 4.4

of FIG. 2 and illustrates .to :advantage the low and high pressure sides ofthe loading plate and the pressure loading cavities.

.Attention now is directed to the drawings wherein like numerals of reference designate like parts throughout the several views. .The gear pump ofthe present invention .comprises .a .housing 10 having formed therein substantially cylindrical, parallel chambers 11 and 12 which intersect along a chordal plane designated 14. The housing is further provided with cut-away portions 15 and 16 which are formed by cuttingaway portions of the housing adjacent the chordal plane 14. These cut-away portions extendfrom end to end of the housing.

Disposed within the chambers 11 and -12 aredisplacing gears Hand 19, respectively. The gears18 and 19 are in mesh substantially along the chordal plane 14. The gears 18 and 19 are provided with journals 20 which are formed integral therewith. As is best illustrated in FIG. 1, one of-the journals 20 of the gear 18 is extended to form an input or output shaft 21. The shaft 21 is rotated by any suitable means (not shown) to provide a drive for the device when operatedas a pump and serves as an output shaft when operated as a fluid motor. The journals 20 are rotatably supported by means of journal bearings 22 which are so machined as to be a close fit on the journals 29' and within chambers 11 and 12. The journal bearings 22 cooperate with the wallsof the chambers 11 and 12 to define a pumping chamber surrounding the intenneshing gears 18 and 19.

.Thehousing 10 is provided with a pair of passages 24 and 25 (FIG. 2) which intersect the cut-away portions 15 and .1-6. These pass-ages serve alternately as inlet and outlet ports, i.e., one serves as an inlet and the ,otheras an outlet dependent upon the direction of rotation of the gears 18 and 19. The housing 10 is alsoprovided with end covers 26 and 28 which serve to retain the gears 18 and 19 and journal bearings 22 within the housing lthand in pumping relationship.

A loading plate 29 is interposed between the-,right'hand journal bearings 22 (FIG. 1) and the end cover 28. The loading plate .29 is provided with a longitudinal slot.30 within which is received a sealing member 31. An undulating spring 32 is positioned within the slot 30 beneath the member 31 and is adapted to urge the ,memberjrl into sealing engagement with-the end plate v28.

The loading plate 29 is further provided with longitudinal recesses 34 and 35 on opposite sides of the slot 30. A pair of reed-type valve members 36 and 38 are positioned within the recesses .34 and 35, respectively. Valve members 36 and 38 are of the same configuration as, but slightly smaller than, the recesses 34 and 35. A pair of valve springs 39 and 40 are interposed between the valve members 36 and 38, respectively, and the end plate 28jand normally urge the valve members 36 and 38 to their closed positions. The loading plate 29 is further provided with pairs of valve openings 41 and 42 which respectively communicate the recesses 34 and 35 with a low pressure recess 44 formed in the opposite sideof the loading plate 29. The valve openings 41. and 42 are,.of course, closed when the valve members 36 and 38 are in theposition shown in FIGS. 3 and 4.

In order that a better understanding of the invention may be had, its mode of operation will now be described.

For purposes of illustrating the operation of the device as a pump, assume that the input shaft 21, and consequently the gear 18, is rotating in a direction shown by the arrows in FIGS. 1 and 2. The passage 24 thus becomes the inlet port for this direction of rotation and the passage 25 becomes the outlet port. Fluid supplied to the passage 24 will be delivered to the outlet passage 25 in a manner well-known to those skilled in the art and at a pressure determined by the load (not shown) connected to the passage 25.

Since the cut-away portion 16 intersects passage 25, it will fill with high pressure fluid. Some of the high pressure fluid within cut-away portion 16 will flow over the top of the loading plate 29 and into pressure loading cavity 45. The sealing member 31 is made of such a thickness as to fit within the slot 30 and of such a length as to firmly engage the walls of the bores 11 and 12. Thus the sealing member 31 confines the high pressure fluid to the right-hand side of the loading plate 29 as viewed in FIG. 2. The force exerted by the spring 32 serves to provide an initial loading of the journal bearings and maintains sealing member 31 in contact with cover 28 prior to the introduction of high pressure fluid into the cavity 45.

The high pressure fluid present within the cavity 45 exerts a force on the adjacent journal bearings 22, through the loading plate 29, and urges them into close contact with the side faces of the gears 18 and 19. Since the high pressure fluid in the cavity 45 acts on only one-half of the loading plate 29, the effect is to produce a loading of the journal bearings 22 which is known in the art as ofii-set pressure loading.

The high pressure fluid in the cavity 45 is precluded from passing through the valve openings 42 and into the low pressure cavity 44 by the closed condition of the valve member 38. The valve member 38 is normally held in this position by the valve spring 40 so the high pressure fluid in the chamber 45 only supplements the action of the spring 40.

During normal operation of a pump or motor of this type, it is inevitable that minute quantities of the fluid being pumped will leak across the side faces of the pump ing gears and thence through the journal bearings along the journals. To accommodate this leakage fluid, the end plate 26 is provided with a low pressure cavity 46. The low pressure cavity 44 formed in the loading plate 29 serves the same purpose at the opposite ends of the gears 18 and 19.

The gear 19 is provided with an internal bore 48 extending axially therethrough and interconnecting low pressure cavities 44 and 46. Should sufficient fluid accumulate in the cavities 44 and 46 and bore 48 to cause a rise in pressure therein, this accumulation will be relieved by the opening of the valve member 36. The valve spring 39 is so selected that slight pressure on the under side of the valve member 36 will open this valve. The leakage fluid in the cavity 44 will then flow through the valve openings 41 and into a chamber 49 similar to pressure loading chamber 45. From here the leakage fluid can then flow back to inlet through the passage provided by the cut-away portion 15.

The chamber 49 and cut-away portion 15 will be filled with fluid at inlet pressure so that the valve member 38 will only open when the pressure within the cavity 44 exceeds the combined force exerted on the valve member 36 by the spring 39 and the fluid within the chamber 49.

Due to the symmetrical construction of the apparatus, it is obvious that the mode of operation as a pump will be identical should the direction of rotation of the input shaft 21 be reversed. In this instance however, the chamber 49 will become the pressure loading chamber and access? the chamber 45 will become the low pressure chamber. Also, the passage 24 will now become the outlet while the passage 25 becomes an inlet. Furthermore, the valve member 38 rather than the valve member 36 will now function to relieve an excess accumulation of leakage fluid within the low pressure cavity 44.

If the device is to be operated as a motor, pressurized fluid will then be applied to either the passage 24 or the passage 25, dependent upon the direction of rotation desired of the shaft 21 which would then become an output shaft. The device will then operate as a motor in a manner well-known to those skilled in the art. The valves 36 and 38 would function in the same manner as when the device were driven as a pump with one of the valves checking the flow of high pressure fluid into the cavity 44 while the other valve relieved an excess accumulation of leakage fluid within the cavity 44.

It should be obvious that the present invention provides a hydraulic device capable of being operated in either of two directions as either a hydraulic pump or a hydraulic motor. Because of the symmetrical design, the volumetric, mechanical, and overall efficiencies will be identical for either direction of rotation when the device is operating as a pump or a motor. Off-set pressure loading is provided for either direction of rotation and provision has been made to accommodate leakage through the journal bearings regardless of either the direction of rotation or the nature of the operation, i.e., as a pump or as a motor.

It is to be understood that the above described arrangement is simply illustrative of the principles of the present invention. Numerous modifications can be readily devised by those skilled in the art which would still embody the principles of the present invention and fall within the spiirt and scope thereof.

What is claimed is:

1. A pressure loaded gear pump or motor comprising a housing having therein a pair of substantially cylindrical chambers intersecting along a chordal plane, a pair of intermeshing displacing gears disposed for rotation within said chambers, a plurality of journals formed integral with said gears and extending axially therefrom, a journal bearing rotatably supporting each of said gear journals, said journal bearings cooperating with said housing to define a pumping chamber surrounding said gears, said housing having a pair of fluid ports formed in opposite sides thereof along said chordal plane and intersecting said pumping chamber, a first cover secured to one end of said housing for retaining said gears and said journal bearings within said housing, a second cover secured to the other end of said housing and cooperable with said first cover for retaining said gears and said journal bearings in pumping relationship, a loading plate interposed between one of said covers and the adjacent journal bearings and spaced from said cover, a sealing member interposed between said loading plate and said cover to define a pair of congruent pressure loading chambers, means defining passages connecting each housing port with the adjacent pressure loading chamber, means defining a low pressure cavity in the surface of said loading plate adjacent said journal bearings, and a pair of valves disposed in said loading plate on each side of said sealing member, said valves serving as check valves to preclude fluid flow from said pressure loading chambers to said low pressure cavity and as relief valves to enable fluid flow from said low pressure cavity to said pressure loading chambers.

2. A pressure loaded gear pump or motor as defined in claim 1 wherein said pair of valves are spring loaded.

3. A pressure loaded gear pump or motor as defined in claim 1 wherein said valves comprise flat reeds, and resilient means are interposed between said reeds and said cover to normally urge said valves to a closed position.

4. A pressure loaded gear pump or motor as defined in claim 1 wherein said valves comprise flat reeds positioned within matching recesses in said loading plate, and arcuate leaf springs are interposed between said reeds and said cover to normally urge said valves to a closed position.

5. A pressure loaded gear pump or motor as defined in claim 1 wherein resilient means are interposed between said sealing member and said loading plate to provide an initial load on said bearings.

6. A pressure loaded gear pump or motor as defined in claim 1 wherein said loading plate is provided with a longitudinal groove for reception of a sealing member of rod-like configuration, and an undulating spring is interposed between said sealing member and the bottom of said groove to provide an initial load on said bearings.

7. A pressure loaded gear pump or motor as defined in claim 1 wherein the other of said covers is provided with a low pressure recess adjacent said gear journals, and one of said gears is provided with an axial bore therethrough interconnecting said low pressure recess and the low pressure cavity in said loading plate.

References Cited in the file of this patent UNITED STATES PATENTS 

